1. Field of Invention
The present invention relates to the use of Maillard reaction products as adjuvants in a variety of applications, including in separation processes, and especially in connection with the selective separation of solids and/or ionic species from aqueous media, such as in the process of flotation. The invention also provides novel materials for use in such applications.
2. Description of Related Art
Flotation is a widely used separation process designed for the recovery or isolation of a valued material present in admixture in a liquid suspension or dispersion (and especially aqueous suspensions or dispersions). Separation is accomplished based on differences in the tendency of various materials to associate with rising gas (usually air) bubbles.
Various additives are commonly incorporated into the flotation liquid (e.g., the aqueous suspension or dispersion) to improve the selectivity of the separation process.
For example, substances identified as “collectors” can be used to chemically and/or physically absorb preferentially onto one of the substances in the suspension or dispersion (often, though not always the valued material in the suspension or dispersion) to render it more hydrophobic and more amenable to flotation.
Conversely, “depressants,” are often used in conjunction with collectors, to render other materials in the suspension or dispersion (often though not always the less valued material in the suspension or dispersion, e.g., gangue) less likely to associate with the air bubbles, and therefore less likely to be carried into the froth concentrate and more likely to remain in the underflow or tailings. Various depressants for improving flotation separations are known in the art and include guar gum, sodium silicate, starch, tannins, dextrins, lignosulphonic acids, carboxymethyl cellulose, cyanide salts and others.
Because different substances in the suspension or dispersion are affected differently by the “collector” and/or the “depressant,” a degree of separation is obtained by this process.
The manner in which known collectors and depressants achieve their effect is not understood with complete certainty, and several theories have been proposed. Depressants, for example may interfere with or prevent one of the substances in the suspension or dispersion (such as gangue) from adhering to another of the substances in the suspension or dispersion (such as a valued material to be recovered), or the depressant may interfere with or even prevent the collector(s) from absorbing onto one of the substances (such as the gangue). Whatever the mechanism, however, the ability of a depressant to improve the selectivity in a flotation process can very favorably impact the economics of the process.
Flotation is practiced in the beneficiation of a wide variety of valued materials, including the recovery of minerals (e.g., phosphorous and potassium) and metal ores (e.g., platinum group elements), the recovery of high molecular weight hydrocarbons such as bitumen from sand and/or clay, and the separation of coal from its ash content to name a few, to obtain the removal of unwanted contaminants, which are unavoidably co-extracted from natural deposits, from the valued material.
In the case of solid ore beneficiation, the use of flotation generally comprises grinding the crude ore into sufficiently small, discrete particles and then contacting an aqueous “pulp” of this ground ore with rising air bubbles, typically while agitating the pulp. Prior to flotation, the crude ore may be subjected to any number of preconditioning steps, including selective crushing, screening, desliming, gravity concentration, electrical separation, low temperature roasting, and magnetic differentiation.
In addition to flotation, a number of other processes also are designed for the separation of solid contaminants from liquid suspensions or dispersions. Like flotation these other processes also often take advantage of additives that facilitate the desired separation, either by destabilizing the suspension or dispersion, or by otherwise causing contaminants in the suspension or dispersion to form larger agglomerates. Coagulation, for example, refers to the destabilization of suspended solid particles, such as by neutralizing the electric charge that separates them. Flocculation refers to the bridging or agglomeration of solid particles together into clumps or flocs, thereby facilitating their separation by settling or flotation, depending on the density of the flocs relative to the liquid. Otherwise, filtration may be employed as a means to separate the larger flocs.
Flocculants, such as acrylic polymers, find application, for example, in the separation of solid particles of rock or drill cuttings from oil and gas well drilling fluids, for agglomerating clays suspended in the waste slurry effluent from phosphate production facilities, in coal slurry dewatering, for treating sewage to remove contaminants (e.g., sludge) via sedimentation, for processing of pulp and paper mill effluents to remove suspended cellulosic solids, for removing sand from aqueous bitumen-containing slurries generated in the extraction and subsequent processing of oil sands, and for removing suspended solid particulates in the purification of drinking (i.e., potable) water.
The foregoing descriptions are illustrative of specific examples where an aqueous liquid suspension or dispersion is processed to recover, isolate, separate, or purify a desired valued material. Such separations also are common in a number of other water-consuming industries and the present invention is intended to be applicable to the wide variety of treatment options designed to recover, isolate, separate, or purify a desired valued material from unwanted contaminants. It may also be used to remove unwanted contaminants from a liquid, such as in water purification.
In particular, the present invention is directed to the discovery of a variety of new uses for certain known materials, as well as to the discovery of new classes of materials which can be effectively employed in a wide range of applications including, but not limited to a variety of separation processes, including flotation. Applicants have determined that the materials of the present invention have utility as adjuvants for effectively enhancing the performance of a wide variety of processes, such as the selective separation of a wide variety of solid contaminants from liquid suspensions and dispersions.